Rotary piston engine with trochoidal construction

ABSTRACT

This invention relates to an improvement in a rotary piston engine, of trochoidal construction, wherein for pairing reasons the formation of the housing and the piston rotor is based not only upon the trochoid but also upon the inner or outer envelope curve branches being coordinated thereto, and wherein the gas check between two adjacent working spaces or chambers is effected by means of radial packing strips; the improvement comprising that the housing and piston rotor delimitations consist of a pair of parallel curves on the same side, facing away from the radial packing strip, of the gemoetrically exact curve and extending equidistantly with respect thereto.

United States Patent [191 Huf [ ROTARY PISTON ENGINE WITH TROCHOIDAL CONSTRUCTION [75] Inventor: Franz Hui, Konstanz, Germany [73] Assignee: Dornier System GmbH,

Friedrichshafen/Bodensee, Germany [22] Filed: Dec. 6, 1971 [21] Appl. No.: 204,918

[30] Foreign Application Priority Data Oct. 9, 1973 Primary ExaminerCarlton R. Croyle Assistant Examiner-Richard E. Gluck Attorney-James E. Bryan [5 7 ABSTRACT This invention relates to an improvement in a rotary piston engine, of trochoidal construction, wherein for pairing reasons the formation of the housing and the piston rotor is based not only upon the trochoid but also upon the inner or outer envelope curve branches being coordinated thereto, and wherein the gas check between two adjacent working spaces or chambers is effected by means of radial packing strips; the improvement comprising that the housing and piston rotor delimitations consist of a pair of parallel curves on the same side, facing away from the radial packing strip, of the gemoetrically exact curve and extending equidistantly with respect thereto.

3 Claims, 6 Drawing Figures I PAIENIEDUEI M975 SHEET 18F 3 I NVENTOR FRANZ HUF 9M) %M AT ORNEY PATENTED [1m 9 1973 SHEET 2 BF 3 INVENTOR FRANZ HUF aw Z- @041 ATTORNEY PATENTEDUEI e um SHEET 3 BF 3 INVENTOR FRANZ HUF yawiw ATTORNEY ROTARY PISTON ENGINE WITH TROCHOIDAL CONSTRUCTION This invention relates to a rotary piston engine, and more particularly to a rotary piston internal combustion engine with trochoidal contruction. In these machines it is a trochoid, and specifically either an epitrochoid or a hypotrochoid, that forms the basis for the design. This type of rotary piston engines can be categorized in two groups: In one group, the inner envelope curve is taken as the trochoid, and in the other group it is the outer envelope curve and, respectively, the branches of the envelope curve, which are employed in order to make up or form the structural machine elements, i.e. housing and piston rotor. In this connection it is immaterial for the investigations involved here which part of the machine is stationary and which is rotary, whether it be the housing or the piston, or whether possibly both machine elements rotate with respect to a reference system being rigidly disposed in space.

For structural reasons it is necessary that a gap be provided between the piston rotor and the housing. Thus the geometrically exact curves, i.e. the trochoids and/or the branches of the envelope curves, cannot be employed for the two structural elements. On the basis of the exact curve shape, one structural part, for example the housing, was hereto fore in practice customarily slightly widened outwardly, and the other structural element, for example the piston rotor, was slightly reduced inwardly. The delimitations of the structural elements that were produced in this manner extended equidistantly with respect to the geometrically exact curve, i.e. with respect to the trochoid and/or the envelope curve thereof. An equidistant curve trace or course means that parallel curves are produced which have universally the same distance normal to the trochoid. In the example mentioned hereinabove in which the parallel curve is widened or expanded as compared to the exact curve, the delimiting lines are positioned outside of the exact curve path, and the delimiting line itself represents a longer curve path than the exact starting curve (the trochoid). Analogously, parallel curves also can extend within the geometrically exact curve. For the sake of simplicity, the outwardly extending longer parallel curve paths will hereinafter be designated as plus equidistants while the inwardly extending shorter parallel curve paths will be referred to as minus equidistants." Within the framework of these deliberations, it is immaterial whether the basis of the parallel curve paths is the trochoid, or the inner and/or outer envelope curve, or the envelope curve branch thereof.

Naturally a gap between structural elements is harmful in a machine, and here, a gap between the housing and the piston rotor involves problems with respect to the compression and the gas check or sealing effect. In order to obtain a high compression, the gap should be kept as small as possible. On the other hand, a small gap results in difficulties with regard to the radial packing strips or seals. In rotary piston engines, radial packing strips are mounted between two adjacent working spaces or chambers in order to create the gas check or sealing effect between the working spaces or chambers. Disadvantages and difficulties will arise in actual practice, however, because the packing strips must glide with the edge thereof on a structural element of the machine and at that time, during the rotation thereof, are

inclined in constant change at a varying angle with respect to the gliding surface. The result thereof is an uneven wear and tear; canting of the packaging strip in the bed thereof and, as a further consequence, the destruction of the packing strip itself may soon follow. A certain remedial measure might be possible by providing for knife-edge-sharp packing strips, but this solution also fails in view of practical difficulties inasmuch as such strips hardly can be realized in actual practice.

The present invention was based on the objective of creating a high-compression rotary piston engine of trochoidal construction while eliminating the difficulties outlined above pertaining to the gas check or sealing effect. The present invention starts from the premise or concept that in the aforementioned trochoidal machines also the inner or outer envelope curve branches assigned to the trochoid be used in addition to the trochoid, for pairing reasons, as a basis for the provision or formation of the housing and the piston rotor. This object is obtained, in accordance with the present invention, by virtue of the fact that the delimitation of the housing and the piston rotor consists of a pair of parallel curves on the same side facing away from the radial packing strips of the geometrically exact curve (trochoid and/or envelope curve) and extending equidistantly with respect thereto. According to a further characteristic of the present invention, the distance of the parallel curve extending equidistantly with respect to the trochoid is greater than the distance of the parallel curve extending equidistantly to the envelope curve.

According to a further embodiment of the present invention, the radial packing strips are rounded off semi-cylindrically at the side thereof resting against or making contact with the coordinated gliding surface, and the center of the rounding is positioned on the geometrically exact trochoid, while the radius of the rounding corresponds to the greater one of the two equidistant distances of the pair of parallel curves. The essential idea of the present invention thus is that, in such a pairing system, the so-called simultaneous points of the trochoid are positioned in the center of the radial packing strip rounding. The two structural machine parts or elements, namely the housing and the piston rotor, are parallel curves with respect to the geometrically exact curve and are both positioned on the same side of the exact curve. On which side the curve and, respectively, of the trochoid the two parallel curves extend depends only upon the direction in which the radial packing strips are disposed, viewed from the trochoid, i.e. either within or outside of the trochoid. As a result, in pairings with a trochoid and an inner envelope curve, a pair of parallel curves extending outside of the exact curve constitutes the housing and piston rotor delimitation, since in this pairing arrangement with the inner envelope curve the radial packing strips are disposed within the trochoid. In pairing arrangements with the outer envelope curve, on the other hand, the radial packing strips are positioned outside of the trochoid and the pair of parallel curves extends within the geometrically exact curve path. The two aforementioned cases have validity irrespective of whether epitrochoids or hypotrochoids are considered. Those parallel curve paths which extend outside of the geometrically exact curve will be designated as plus equidistants" hereinafter, while parallel curve paths within the geometrically exact curve will be referred to as minus equidistants.

The present invention affords the advantage that the gap between the housing and the piston rotor can be kept very small, i.e. that a high compression can be attained, while the radial packing strip can nevertheless be made in a sufficient strength or thickness and with an exact rounding or roundness. For this reason, the wear and tear of the packing strips is completely uniform, and the disadvantages mentioned hereinabove with respect to damages and even destruction of the packing strip are effectively prevented. The inventive idea is simple to carry out structurally and holds up under a mathematical check since the working spaces or chambers and, respectively, the combustion chambers and the harmful extent of the gap can be accurately calculated.

The inventive concept can be readily employed and applied to all trochoidal shapes, i.e. epitrochoids and hypotrochoids of every category, and equally in each pairing system, i.e. both with troghoids with outer enve; lope curve and with trochoids with inner envelope curve. The sealing system is in no way impaired. An additional advantage of the present invention resides in .that the mutually coordinated structural elements, i.e.

the housing and the piston rotor, with their different equidistants being, however, characterized bythe same signs can be made on the same grinding machine. The following are indicated as exemplary for the application or use of rotary piston engines of the type described herein: internal combustion engines, pumps, or steam engines of any size.

Two embodiments of the present invention will not be further described hereinafter in connection with, and with reference to, the accompanying drawings wherein FIG. 1 illustrates an epitrochoid l l with outer envelope curve;

FIG. la illustrates a segment from FIG. 1 at an enlarged scale;

FIG. 2 illustrates an epitrochoid 2 1 with inner envelope curve;

FIG. 2a illustrates a segment from FIG. 2 at an enlarged scale;

FIG. 3 illustrates a hypotrochoid 6 l with inner envelope curve, and

FIG. 3a illustrates a segment from FIG. 3 at an enlarged scale.

FIGS. 1 and 1a illustrate an example for the pairing arrangement of a trochoid with outer envelope curve. The simplest trochoid, namely the epitrochoid l l (the cardioid), has been chosen for this instance. The figures serve merely for explaining the respective relationships; they are not intended to fix or define the actual orders of magnitude either with respect to the absolute gap width or with respect to the size of the individual equidistant distances.

The epitrochoid l l is shown in dash-dotted lines in FIG. 1 and identified with reference symbol T1. In addition to this geometrically exact trochoid the assigned outer envelope curve I-I has also been represented therein in dash-dotted lines. The outer envelope curve consists of two envelope curve branches, and in the epitrochoid l 1 shown herein, the right envelope curve branch coincides with the trochoid proper. It is for this reason that in the right-hand portion of FIG. 1 the designation of the outer envelope curve has been placed in parentheses behind the designation T1 of the trochoid. As has already been mentioned hereinbefore, the trochoid T and the outer envelope curve l-I are geometrically exact curve paths. In the pairing arrangement chosen in this case, the radial packing strips D are positioned outside the trochoid. For this reason, parallel curves are devised or projected on the opposite side, i.e. within the trochoid, for the delimitations of the housing and the piston rotor. The parallel curve for the housing has been drawn in as a solid line and is characterized with reference symbol G. It extends at the distance ('Z'G from the envelope curve H and, respectively, the trochoid T The second parallel curve represents the delimiting line for the piston rotor. It is shown in dashed lines and is characterized with reference symbol K. It extends at the distance ri' from the trochoid T The definitions z'z' and a'z' are intended to express, by virtue of their sign, that what is involved in this particular case are the aforementioned minus equidistants.

It is apparent from the enlarged showing of FIG. 112 that the radial packing strip D is rounded off semicylindrically at the end thereof. The cylinder axis extends through the simultaneous point S and is thus positioned on 'tfixa&&&fi id.fi radius ofthe packing strip rounding corresponds precisely to the greater equidistant of the pair of parallel curves in this case the piston rotor equidistant zi As an effective gap there thus remains-only the difference between the two equidistants (Z, and (1' This gap therefore can be kept very small while, nevertheless, the rounding or roundness of the radial packing strip D can be made with a sufficiently large radius.

FIG. 2 illustrates the example of a pairing of a trochoid with inner envelope curve for the case of an epitrochoid 2:1 (the reniform curve). Here again, the trochoid has been shown in dash-dotted lines and is characterized or identified with reference symbol T In order to insure greater clarity of illustration, the coordinated geometrically exact inner envelope curve has not been shown in FIG. 2, but only in FIG. 2a. It has therein equally been illustrated as a dash-dotted curve and is identified in this instance with reference symbol H The trochoid T and the inner envelope curve H both extend through the simultaneous point S which constitutes in this case, analogously to the example of FIG. 1a, the axis of the semi-cylindrical rounding of the packing strip D. In this particular pairing arrangement, the packing strip is mounted within the trochoid so that the parallel curves for the housing and piston rotor delimitations must be chosen on the other side, i.e. outside of the mathematically exact curve. The parallel curves extend here again with the distances +5 (between trochoid T and housing G) and +t'i (between inner envelope curve H, and piston rotor K) from the geometrically exact curves. The sign symbolizes in this case that what is involved are the-aforementioned plus equidistants. I

Essential for the present invention is here again the fact that both parallel curve paths are positioned on the same side of the geometrically exact curve, i.e. that two plus equidistants must be present.

FIG. 3 disciassasa'rii'rther embodiment of the present invention a hypotrochoid 6: l with inner envelope curve This pairing arrangement corresponds to the machine design by Sensaud de Lavaud. Here again, a portion has been shown at an enlarged scale in FIG. 3a.

The hypotrochoid has been represented once again in dash-dotted lines as a mathematically exact curve. It is identified with reference symbol T Also the coordinated mathematically exact inner envelope curve H, has been shown in dash-dotted lines Both the trochoid and the envelope curve extend again through the simultane'ous point S. The provision also has been made in this case that the axis of the semi-cylindrical packing strip D extends through S. As a parallel curve to the geometrically exact hypotrochoid T the housing wall G extends in the distance of +5 as a parallel curve to the inner envelope curve H the piston rotor delimitation K, being shown in dashed lines, extends in a distance of +11}. Both parallel curves are positioned on the same side of the hypotrochoid, namely outside of the geometrically exact curve. It follows accordingly as has also been expressed by virtue of the sign of the equidistants that what is involved in this case are the aforementioned plus equidistants. As an effective gap between the housing and the piston rotor there remains the difference z'z' It will be obvious to those skilled in the art that many modifications may be made-within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

l. A rotary piston engine of trochoidal construction, comprising; two major structural elements corresponding to a piston and a housing enclosing said piston, respectively, said structural elements forming working chambers between them, one of said structural elements having a shape corresponding exactly to a curve parallel to a geometrically exact trochoid, the other of said structural elements having a shape corresponding exactly to a curve parallel to a geometrically exact envelope curve of said trochoid, the distance of said curve parallel to said trochoid from said trochoid is greater than the distance of said curve parallel to said envelope curve from said envelope curve and both of said parallel curves are on the same side of one of said trochoid and said envelope curve and radial sealing strips, said sealing strips being mounted on said structural element having a shape corresponding to a curve parallel to said envelope curve, adapted to slide on said structural element having a shape corresponding to a curve parallel to said trochoid and form a seal between each pair of adjacent working chambers, positioned on the side of one of said trochoid and said envelope curve opposite said two parallel curves and having that portion, which slides on said structural element having a shape corresponding to a curve parallel to said trochoid, formed as a semi-cylinder whose radius is equal to said distance of said curve parallel to said trochoid from said trochoid and whose axis passes through said trochoid at the point of intersection of the inner and outer envelope curves of said trochoid.

2. A rotary piston engine according to claim 1 wherein the structural element having a shape corresponding to a curve parallel to an envelope curve of the trochoid has a shape corresponding to a curve parallel to a geometrically exact inner envelope curve of said trochoid.

3. A rotary piston engine according to claim 1 wherein the structural element having a shape corresponding to a curve parallel to an envelope curve of the trochoid has a shape corresponding to a curve parallel to a geometrically exact outer envelope curve of said 

1. A rotary piston engine of trochoidal construction, comprising; two major structural elements corresponding to a piston and a housing enclosing said piston, respectively, said structural elements forming working chambers between them, one of said structural elements having a shape corresponding exactly to a curve parallel to a geometrically exact trochoid, the other of said structural elements having a shape corresponding exactly to a curve parallel to a geometrically exact envelope curve of said trochoid, the distance of said curve parallel to said trochoid from said trochoid is greater than the distance of said curve parallel to said envelope curve from said envelope curve and both of said parallel curves are on the same side of said trochoid and said envelope curver, respectively and radial sealing strips, said sealing strips being mounted on said structural element having a shape corresponding to a curve parallel to said envelope curve, adapted to slide on said structural element having a shape corresponding to a curve parallel to said trochoid and form a seal between each pair of adjacent working chambers, positioned on the side of one of said trochoid and said envelope curve opposite said two parallel curves and having that portion, which slides on said structural element having a shape corresponding to a curve parallel to said trochoid, formed as a semi-cylinder whose radius is equal to said distance of said curve parallel to said trochoid from said trochoid and whose axis passes through said trochoid at the point of intersection of the inner and outer envelope curves of said trochoid.
 2. A rotary piston engine according to claim 1 wherein the structural element having a shape corresponding to a curve parallel to an envelope curve of the trochoid has a shape corresponding to a curve parallel to a geometrically exact inner envelope curve of said trochoid and is outside said envelope curve and the structure element having a shape corresponding to a curve parallel to said trochoid is outside said trochoid.
 3. A rotary piston engine according to claim 1 wherein the structural element having a shape corresponding to a curve parallel to an envelope curve of the trochoid has a shape corresponding to a curve parallel to a geometrically exact outer envelope curve of said trochoid and is inside said outer envelope curve and the structural element having a shape corresponding to a curve parallel to said trochoid is inside said trochoid. 